1. Field of the Invention
Aspects of the invention relate to technology that can adaptively control an access mode that is used for uplink communication and downlink communication in a communication system using an unlicensed band or a shared band.
2. Description of the Related Art
As demand for a high speed communication service with excellent quality increases, radio resources available for the communication service are being drained. Frequency resources with good communication efficiency are limited, while communications services requiring frequency resources are on the increase. Accordingly, research regarding cognitive radio technology that can more effectively use radio resources is actively being conducted.
The cognitive radio technology can be applicable to an unlicensed band or a shared band, such as Industrial, Scientific, and Medical (ISM) bands. Although the cognitive radio technology is applied, a secondary system using the cognitive radio technology should prevent collisions with a primary system. When a plurality of secondary systems exists, it may be necessary to improve the usage efficiency of radio resources for the secondary systems. Accordingly, there is a need for technology that can more effectively apply cognitive radio technology to improve the usage efficiency of radio resources.